The present invention relates generally to dewatering apparatus of the type adapted to screen solids from a solids containing liquid slurry and, more particularly, to a dewatering apparatus of the type wherein the separation is effected by passing the solids containing slurry over the surface of a screen through which a substantial portion of the liquid in the slurry passes while the solids in the slurry can not pass through the openings in the screen.
The basic dewatering apparatus of the type to which the present invention relates is disclosed in U.S. Pat. No. 2,916,142 issued to Freerk J. Fontein. As disclosed therein, a solids containing slurry is supplied to the inlet end, i.e., upper edge, of an arcuate screen, commonly termed a sieve bend, to flow downwardly over the concave surface of the arcuate screen in a substantially tangential direction. A substantial portion of the liquid in the slurry and any undersize solids pass through the openings in the screen and are collected as a low solids underflow. The oversize solids in the slurry continue to flow over the concave surface of the screen under the force of gravity to the discharge end, i.e., lower edge, of the screen and are collected as a concentrated solids overflow.
A modern adaptation of this basic dewatering apparatus is shown in U.S. Pat. No. 4,519,902 issued to Greever C. Kinder. Disclosed therein is a dewatering apparatus incorporating a screening member having an arcuate sieve bend upper portion which discharges onto a lower flat portion. The screening member is mounted directly to a support frame which forms the main body of the apparatus. To enhance the flow of slurry over the screening member, the support frame is operatively connected to a vibrating means which imparts a vibratory motion to the screen surface. It is said that the vibratory motion results in a further dewatering of the slurry therefor providing a more concentrated overflow.
In both of the aformentioned patents, a unitary screen member is provided having a screen surface formed of a plurality of spaced bars which extend transversely in a direction generally perpendicular to the direction of slurry flow downwardly over the screen surface. The bars are spaced apart a distance less than their width to form slit-like openings in the screen member between adjacent bars having a predetermined desired width so as to provide the desired straining effect. The bars may be rectangular, trapezoidal, or triangular in cross-section.
As noted in the aforementioned patents, it is desirable that the screen member of this type of dewatering apparatus be designed to be reversible so that the original inlet end of the screen member becomes the discharge end and vice-versa. Since the greatest wear is on the leading edge, with respect to slurry flow over the screen surface, of the screen bars forming the screen member, a more uniform wear on the screen member can be obtained by reversing the screen member thereby prolonging the life of the screen member.
In order to permit the screen member to be reversed, it is necessary that the screen member be designed to be removably mounted to the dewatering apparatus. In U.S. Pat. No. 4,519,902, the screen member is held in place by a wedge assembly which comprises a wooden member and a clip which secure the screen member at various positions along its lateral edges to the side flanges of the dewatering apparatus. It is also known in the art to form the screen member itself with lateral flanges which extend upwardly along the sides of the screen surface. The flanges are bolted to the lateral flanges of the dewatering apparatus to securely, yet removably hold the screen member in place.
However, in practice screen members secured in the manners previously described are often difficult to remove and reverse. It is not uncommon for the frame of the dewatering apparatus to be constructed for cost reduction purposes of materials which are subject to corrosion by the slurry flow. Typically, it requires two men four to five hours to remove and reverse a screen member of this type which has been bolted to the frame of the dewatering apparatus.